The present invention relates to a method and a device for trenchless pipe laying underground.
In the past numerous different methods and devices have been developed in order to lay pipes trenchless underground to pass under sensitive surface areas for which pipe laying in an open trench was not possible or was not recommended due to technical, ecological, legal, or economical reasons. This can be the case e.g., where the surface within the laying area can not be driven on by heavy construction machinery (e.g. swamps, waters) or where from a ecological view point no building permit can be given (e.g. in protected areas), or where the application of conventional laying techniques would be too expensive (e.g. in case of large laying depths and high groundwater levels).
In literature there exist comprehensive works of implemented and established methods (z. B. Stein, D., Grabenloser Leitungsbau, 2003 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin, ISBN 3-433-01778-6). A classification of the procedures may be based on the controllability (steer/uncontrolled procedures), the soil treatment (soil displacement/soil withdrawal), the drill cuttings transport (mechanically, hydraulically), as well as the number of work steps (pilotbore, reaming pass, pull in or pullback step). Further distinguishing features are e.g. the fundamental geometrical forming of the drilling axis (straight-lined, curved) as well as by means of the respective methods for laying different pipe materials (e.g. concrete, polyethylens(PE), casting, steel etc.). In addition also the attainable drilling dimensions (length, diameter, volume) serve to classify the methods.
A procedure well-known from the state of the art is the steerable horizontal drilling technology (flush drilling method, horizontal directional drilling (HDD). With this three-phase procedure (pilotbore, reaming pass, pull in or pullback step) only pipeline of high tensile strength (e.g. made of steel, PE or casting) can be laid. The geometrical laying output may be over 2.000 m in length and the attainable pipe diameters are maximally approx. 1,400 mm.
Although the steerable horizontal drilling technology has been proven world-wide as a reliable laying method in suitable grounds, there are nevertheless ecological, technical, and economical disadvantages associated with this method.
On both sides of the obstacle to be undercrossed large work surfaces (some thousand square meters) are necessary (so called (rig site and pipe site). These surfaces in particular in ecologically sensitive areas, are not always present or may have an adverse negative influence on the environment.
A further well-known method is microtunneling (MT). A steered, possibly curved, bore is typically produced from a starting pit or a starting excavation to a goal pit or a goal excavation. Characteristic to this method is that pilotbore, reaming pass, pull in or pullback step of the pipes are accomplished in one work step. This combined work step is accomplished in principle by pushing or pressing from the pit or the starting excavation. The drilling pipes, which are also the production pipes, are not tensily connected. With the MT procedure drilling lengths over 500 m and borehole diameters of more than 2,000 mm can be achieved.
A further disadvantage of this method is e.g. that the pushing pipes usually made of concrete remain in the bore causing high costs for the production of the bore. The use of steel or PE-pipes with MT is in principle possible but unusual due to the technical difficulties connected therewith. PE-pipes e.g. have a low compressive strength limiting directly the possible drill length. Steel pipes are axially highly strainable but have to be attached one by one by welding in the starting area. Therefore applications such as high pressure pipelines as an oil or a gas pipeline are typically not possible.